300 testers doesn't sound too low a number, however, based on some of the technical issues that some people you've got to wonder was there much variety in the hardware mix that those testers use.
For the game play issue, were they getting much feedback from the testers or if most of the testers were just wanting to play the game and didn't give any real feedback.
Does Slitherine/Matrix have any other high end games like this. I can think of Command, but I'm not sure it pushes the envelope this much.
Here is where I'm disappointed at with DW2 at this time. DW2 seems to be just a new version of DWU with new graphics engine and GUI. I'm not seeing anything that's new to the game. The story line looks like it's going to be the same from DW2. All of the old game mechanics are there with a few tweaks, but nothing major. And in a few cases, they seem to have taken a step back. Maybe I (we) had too many high hopes for DW2. Maybe after having played Stellaris for years now has tainted us. Take research as an example. DW2s big new change is hiding tech. That's good for about 1 play through. Compare that to Stellaris random research choices, which, even going back to an earlier save your not guaranteed the same choices. Or the camera, as Martok pointed out. in Stellaris you can pan 360 degrees on both X and Y axis of an object but not in DW2,
I do like the new GUI for the most part. And I feel like I'm getting enough information out of the game to better understand what's happening in certain areas, like colony net income/loss.